What is SIP PRACK and 100rel
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SIP PRACK and 100rel
SIP PRACK (Provisional Acknowledgement) is a way to enable reliability for SIP 1xx provisional messages like 180 ringing and 183 session in progress
It is defined in rfc3262
PRACK messages flow from calling party to called party, the called party answers the PRACK messages with 200 OK, PRACK message is sent from calling to called party whenever it receives a 1xx messages from called side, as the name suggests it the acknowledgement by the calling side that it has received the 1xx message which was generated by called side
Either calling or called party can include Supported :100rel or Required : 100rel in INVITE or subsequent 1xx message to show that it supports PRACK messages
In case of Required : 100rel It becomes mandatory for other party to send or answer the PRACK messages
One important thing to remember here is that PRACK is only for 1xx messages other than 100 (Trying) as 100 trying responses are hop-by-hop only
One Response to “What is SIP PRACK and 100rel”
In a back 2 2back configuration: When PRACK message is send, is it mandatory to forward the RSec as well ?? (not the CSec, the RSec)
By Jimy on Mar 17, 2010